Process for the preparation of pentaerythritol



Patented May 6 19,41

. UNITED STATE s PATENT. OFFICE .rnoonss non mm ranmmrron or raumanmnmror. I

Joseph A. Wyler. sue-Irwin, Pa., asalgnor to Troian Powder Company, Allentown, Pa.

Ca(OH) 2, or Ba(OI-l i) 2, and although many such processes are described in the literature. the

yields are usually low-approximately 50-60% of theory. In addition to the low yields, further unfavorable factors in these processes are the length of time required to complete the reaction and the formation of a relatively large amount of a dark colored resinous syrup.

It is an object of my invention to increase the yield of pentaerythritol received from a given amount of aldehydes. A further object is to prevent the formation of colored products during the condensation of the, CHzOand the CHaCHO.

Still further objects are to speed up the reaction 1 in the cold and to obtain more uniformand consistent results'for this condensation.

In general, the commercial condensation of CHzO and CHsCHO is based upon the use of 4 to 5 molecules of formaldehyde for each molecule of acetaldehyde in alkaline media, at temperatures not exceeding 50 C., and in such a volume of water as to provide a solution to contain Application March 28, 1940, Serial N0. 326,377

and the dipentaerythritolis formed in accord-- ance with the following reactions:

- n on k H OH Formaldehyde andthat one molecule of A undergoes, decomposition into Home n HOB1CCCH ncoon Home on Formic Acid Pentaerythritol 11 (A) (Unstable) and that two molecules of A undergo decomposition into:

HOHIC H H CHzOH HOHaC-C- O CCH2OH+B2O+2HCOOH HOHzC k CHzOH Dlpentaerythritoi I wish to emphasize that the theory just given is not intended to limit my invention in any way and-that it has been presented in order to conless than 20% of 'aldehydes at the beginning of the reaction.

Although the general reaction for the formation of pentaerythritol is as follows:

the pentaerythritol is generally believed to bet he result of the following reactions:

However, in addition to these reactions others,

producing dipentaerythritol, and sugary, syrupy products also take place, but, as is readily observed, the' reactions above do notexplain the formation of dipentaerythritol which usually forms to the extent of about 10-15% of the pentaerythritoi.

It is possible that some of the pentaerythritol vey a better understanding of the possible function 01 my catalytic agents and of the principles upon which the action of my catalytic agents may be based.

In myprevious applications, S. N. 200,683, and S. N. 270,340 I have disclosed the use of oxalates of Fe, 0o, Cr, Mn, Ni and Cu as well as of Cu, (71120 and Pt as catalytic agents.

I have now discovered that certain are eifective catalysts in the condensation of CI-hO and CHsCHO to C(CHaOHM and and that these acid amides may also be used in combination with the agents disclosed in the applications mentioned above to obtain an additional advantage.

In order to point out my invention more clear-- ly, the following examples, in which all parts are by weight, are given.

Example #1 396 parts of iormaldehyde and 4: {313.115 of acetaldehyde (99%) are mixed with 96.; parts of water-in a suitable container provided with a. stirrer. To this is slowly added, with continued so":

acid amides ring, 53 parts of hydrated lime (low in magnesium) made into a slurry by means of about 100 parts of water. This slurry is added over a period of three to five hours and the reaction mixture is maintained at approximately-20-30. C. throughout the period of addition.

Just before the beginning of the addition of the lime slurry, about 2 parts of formamide are addcdto the condensation mixture.

After all of the lime has been added the stirring is continued at 20-30 C. until an iodinetitration indicates less than, say, 0.10% or aldehydes, calculated to CHaO. The time to arrive at this point varies considerably with the quality of the lime used and other factors. In general 48-72 hours is considered an averagelength of time for the completion of the reaction at the temperature indicated above.

The reaction mixture, at, completion, is treated in the cold with about 10% less sulfuric and than is theoretically equivalent to the lime used. This precipitates most of the lime as calcium sulfate.

'In order to precipitateali or the calcium out of solution, a small amount of oxalic acid is added, in portions, until tests indicate a slight excess present in the mixture. At this stage there will be some sulfate ions in the solution. These are removed by the addition, in small portions, of barium hydrate or barium carbonate, until tests indicate the absence of sulfate ions. This mixture, after a short period of stirring is allowed to settle for several hours or more when the clear supernatant liquor is decanted and the residue- ,flltered. The clear liquors are vacuum evaporated and the pentaerythritol recovered by crystallization. The yield of pentaerythritol plus dimother liquors usually have a yellow-brownish color.

Example #2 Using the same reactants and procedure as given in Example #1, except that 0.25 part-of copper oxalate are added at a stage in the reaction corresponding to 2% hours after the begin-' ning of the lime addition, the time of reaction is considerably reduced. Also, the pentaerythritol and dipentaerythritol obtained as original crystals from this reaction mixture are essentially colorless. The mother liquor obtained from these" crystals is usually practically colorless and is more .pentaerythritol is over 80% of theory and the stable toward heat and oxidizing influences than is the mother liquor made in accordance with Example #1. The yields of pentaerythritcl pluscase, also above dipentaeryfliritol are, in this 80% of theory.

- Example #3 ever, in place of the formamide I may use such water soluble amides as acetamide, propionamide, butyramide. andvaleramide; in place of copper oxalate I may use oxalates of Fe, Co, Cr, Mn, or Ni, which are metals of the first long period Mendelejeffs Periodic System, and in place of metallic copper I may use CuaO or Pt. Also, I may use a larger or a smaller proportion of the acid amide, the oxalate, the oxide, or metal in relation to the aldehydes; or I may use a lower or higher temperature for the reaction, a higher or lower concentration of the reactants, or I may vary the stage at which the various catalysts are added. In short, I may use such operative conditions or details'as would occur to a workman skilled in this art, without departing from the essence of this invention.

I claim:

1. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetaldehyde to pentaerythritol in the presence of a fixed alkali and an aliphatic acid amide containing not more than 5 carbon atoms.

2. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetaldehyde to pentaerythritol in the presence of a fixed alkali, an aliphatic acid amide containing not more than 5 carbon atoms, and an oxalate of a metal of the first long period 01 Mendelejefis Periodic System having an atomic weight between 52 and 63.6.

3. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetaldehyde to pentaerythritol in the presence of a fixed alkali, an aliphatic acid amide containing not more than 5 carbon atoms, an oxalate or a metal of the first long period of Mendelejcfls Periodic System havtotal aldehyde content of the solution being less Using the same reactants and procedure as given in Example #2 and adding about 1 part of precipitated Cu after the condensation reaction had proceeded for a few hours, the time of reaction is still further reduced and good yields of pentaerythritol and dipentaerythritol obtained.

The product is usually white and the mother liq uor obtained is more stable toward heat and oxidative effects than that obtained in either of the previous examples. The greatest single effect ofthe metallic copper is to speed up the reaction for a given temperatur particularly at the final stages of the condensation In this respect it is more eifective than copper oxalate or cuprous oxide.

In the examples, mention was made 'of -formathan 20% by weight. v

5. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetaldehydeto pentaerythritoi in the presence of a fixed alkali,

an aliphatic acid amide containing not more than 6 carbon atoms, an oxalate or a metal or the first long period of Mendelejeffs Periodic System hav-- ing an atomic weight between 52 and 63.8, and a member of thegroup consisting of cuprous oxide and copper; themolecular ratio of the formaldehyde to acetaldehyde being approximately four to one and the total aldehyde content of .the solution being less than 20% by weight.

. 6. The process forthepreparation of pentaerythritol comprising the condensation in aqueous media of formaldehyde and acetsldehy'de to pentaerythrltol in the presence of calcium hydroxide, an aliphaticmcid amide containing not morethanilcarbonatomsandanoxalateoi'a mide, copper oxalate and metallic copper. How- 75. metal of the first-long period or Mendeiejeirs Periodic System having an atomic weight between 52 and 63.6; the molecular ratio of the formaldehyde to the acetaldehyde being approximately fourto one and the total aldehyde content of the A solution being less than 20% by weight; the proportion, by weight, of the metal oxalate to formaldehyde being approximately 0.25 to 119, and

that of the acid amide being 2 to 119.-

'7. The process for the preparation of pentaerythritol comprising the condensation in aqueous media of fonnaldchyde and acetaldehyde to molecular ratio of theformaldehyde to the acetaldehyde being approximately four to one and the total aldehyde content of the solution being less than 20% by weight; the proportion, by weight,

' of the co'pperoz-zalateto formaldehyde being approximately 0.25 to 119 and that oi the formamidebeing 2'to 119. y

- JOSEPH A. WYLER. 

